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In shared Ethernet networks, repeating hubs and associated cabling all reside in a common collision domain. Expanding the network beyond the maximum allowable collision domain results in unstable operation. When expanding 10 Mbps twisted-pair networks, a maximum of four repeating hubs can be cascaded. Each  twisted-pair segment cannot exceed 100 m. No crossover cables are required since the EIM has an internal crossover port 4X. When port 4X is being used, port 4 must remain unused. In this example, the maximum network diameter is 500 m consisting of five 100 m twisted-pair segments and four repeating hubs. |
The restriction that all repeating hubs and associated cabling must reside within the collision domain limits the deployment of fiber optics. However, it is possible to create a network of four repeating hubs and a mix of twisted-pair and fiber optic cabling. The end hubs incorporate twisted-pair cabling, on all ports, while the two inner hubs share a single fiber optic segment which can be up to 2 km in length.  All other twisted-pair segments are limited to 100 m in length. The EI Series does not have any internal crossover ports, so crossover cables are required for hub-to-hub connections. With fiber optics, it is just a matter of reversing one pair of connections. At 10 Mbps, ST fiber optic connectors are used. In this example, the maximum network diameter is 2400 m consisting of four 100 m twisted-pair segments, one 2 km fiber optic segment and four repeating hubs. |
A two-port fiber optic model is available in the EI series, which allows for the cascading of three repeating hubs using two fiber optic segments. In order not to violate the collision domain restriction, the two fiber optic segments cannot exceed an accumulative length of 2 km. The number of cascaded hubs in this configuration should not exceed the three that are shown. A one-port fiber optic repeating hub can be used at the two ends of the network to reduce cost. |
 Switching hubs terminate one end of the collision domain; thereby, simplifying expansion rules. Switches can be cascaded theoretically without limit, as long as each twisted-pair segment is limited to 100 m. In the above example, no crossover cables are used since the EISM has an internal crossover port 5X. When port 5X is being used, port 5 cannot be used. |
 The EISC16 has an internal crossover port 16X which is used to connect to another switch or hub using straight-through cables. If port 16X is used, port 16 cannot be used on the same switch. All twisted-pair segment lengths are limited to 100 m. The EISC has an EIA-232 console port wired as a DTE. In order to connect to either a Windows-based desktop or laptop PC for configuration purposes, a null modem cable not exceeding 50 ft. in length must be used. |
 There are two fiber optic ports on the EISC12 allowing for the cascading of more than two switches using fiber optic cabling. Notice that the crossover function is accomplished over the fiber segment by reversing the connections on one side. The fiber optic ports all operate at 100 Mbps and, therefore, should be configured for full-duplex in order to achieve the maximum segment length of 2 km with multimode fiber and 15 km with single-mode fiber. Connectors for multimode can be either ST or SC. For single-mode, only SC connectors are available. |
By dedicating four ports to a trunk, a high-speed backbone between two EISCs can be created. During configuration, ports are assigned to a trunk in groups of four.  Data between switches is carried over four segments instead of one; thereby, increasing throughput. Like all other twisted-pair segments, length is limited to 100 m and the trunk segments must be crossover cables. More than one trunk can be created for additional cascading at the cost of reduced ports for device connections. |
The EISC is capable of creating either 14 or 15 separate Port VLANs.  Port VLANs allow one physical network to be segmented down to multiple independent "virtual" networks in order to reduce unnecessary traffic, limit broadcast domains and improve security. Each Port VLAN can be expanded using one or more standard hubs or switches and still function independently from the others. The only common connection is through either ports 15 and 16 on EISC. These ports are members of all Port VLAN and could serve as server connections. |
In transparent mode, two EIMCs are connected back-to-back using a fiber optic cable and their DIP switches are set to transparent mode. All other connections are made to copper ports. Hub C can be either a repeating hub or a switching hub. Assume either the hub or the switch is not capable of auto-negotiating. Then the hub and station A will default to 10 Mbps and half-duplex operation. In this case an EIMC-10T/F could be used although an EIMC-100T/F would work equally well. However, if both station A and hub C can auto-negotiate, then the two will do so as if they were directly connected. The fiber optic connection is transparent to the operation. In this situation, the data rate, duplex and flowcontrol will be auto-negotiated. If 100 Mbps operation is expected, either the EIMC-100T/FT or EIMC-100T/FC should be used depending upon the type of connectors needed. An EIMC-10T/F cannot communicate with an EIMC-100T/F since the fiber optic operating wavelengths differ. |
Since two fiber optic ports cannot auto-negotiate, it is necessary to set the data rate and flow rate manually. This situation will occur when an EIMC must mate to a fiber optic port on either a hub or switch. Determine the settings of the fiber optic port on the hub or switch. If it is 100 Mbps, use either the EIMC-100T/FT or EIMC-100T/FC if the port is complying to the 100BASE-FX (1300 nm) standard. However, it is possible that the port supports the new 100BASE-SX (850 NM) standard in which case the EIMC-10T/F must be used in order to properly match the fiber optic operating wavelength. If the data rate is 10 Mbps, then use the EIMC-10T/FT since the port must be complying to the 10BASE-FL (850 NM) standard. Set the duplex mode on the EIMC via the DIP switches to match the duplex operation of the fiber optic port. This is important. With repeating hubs, only half-duplex is possible. To achieve the maximum fiber distance of 2 km at 100 Mbps, the link must be set for full-duplex assuming 100BASE-FX operation. Only the EIMC-100T/FT and EIMC-100T/FC are capable of achieving this distance at this data rate. At 100 Mbps, the EIMC-10T/F is only capable of 300 m; however, at 10 Mbps this same device can span 2 km. |
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